Syscalls for AARCH64 & Syscalls for RISCV

nolibc-open-arm64-riscv.h

/* Syscalls for AARCH64 :
 *   - registers are 64-bit
 *   - stack is 16-byte aligned
 *   - syscall number is passed in x8
 *   - arguments are in x0, x1, x2, x3, x4, x5
 *   - the system call is performed by calling svc 0
 *   - syscall return comes in x0.
 *   - the arguments are cast to long and assigned into the target registers
 *     which are then simply passed as registers to the asm code, so that we
 *     don't have to experience issues with register constraints.
 *
 * On aarch64, select() is not implemented so we have to use pselect6().
 */
#define my_syscall3(num, arg1, arg2, arg3)                                    \
({                                                                            \
    register long _num  asm("x8") = (num);                                \
    register long _arg1 asm("x0") = (long)(arg1);                         \
    register long _arg2 asm("x1") = (long)(arg2);                         \
    register long _arg3 asm("x2") = (long)(arg3);                         \
                                          \
    asm volatile (                                                        \
        "svc #0\n"                                                    \
        : "=r"(_arg1)                                                 \
        : "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
          "r"(_num)                                                   \
        : "memory", "cc"                                              \
    );                                                                    \
    _arg1;                                                                \
})
#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
({                                                                            \
    register long _num  asm("x8") = (num);                                \
    register long _arg1 asm("x0") = (long)(arg1);                         \
    register long _arg2 asm("x1") = (long)(arg2);                         \
    register long _arg3 asm("x2") = (long)(arg3);                         \
    register long _arg4 asm("x3") = (long)(arg4);                         \
                                          \
    asm volatile (                                                        \
        "svc #0\n"                                                    \
        : "=r"(_arg1)                                                 \
        : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
          "r"(_num)                                                   \
        : "memory", "cc"                                              \
    );                                                                    \
    _arg1;                                                                \
})

/************************************************************************/

/* Syscalls for RISCV :
 *   - stack is 16-byte aligned
 *   - syscall number is passed in a7
 *   - arguments are in a0, a1, a2, a3, a4, a5
 *   - the system call is performed by calling ecall
 *   - syscall return comes in a0
 *   - the arguments are cast to long and assigned into the target
 *     registers which are then simply passed as registers to the asm code,
 *     so that we don't have to experience issues with register constraints.
 */

/* https://elixir.bootlin.com/linux/latest/source/tools/include/nolibc/nolibc.h#L1288 */
#if   __riscv_xlen == 64
#define PTRLOG "3"
#define SZREG  "8"
#elif __riscv_xlen == 32
#define PTRLOG "2"
#define SZREG  "4"
#endif

#define my_syscall3(num, arg1, arg2, arg3)                                    \
({                                                                            \
    register long _num  asm("a7") = (num);                                \
    register long _arg1 asm("a0") = (long)(arg1);                         \
    register long _arg2 asm("a1") = (long)(arg2);                         \
    register long _arg3 asm("a2") = (long)(arg3);                         \
                                          \
    asm volatile (                                                        \
        "ecall\n\t"                                                   \
        : "+r"(_arg1)                                                 \
        : "r"(_arg2), "r"(_arg3),                                     \
          "r"(_num)                                                   \
        : "memory", "cc"                                              \
    );                                                                    \
    _arg1;                                                                \
})
#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
({                                                                            \
    register long _num  asm("a7") = (num);                                \
    register long _arg1 asm("a0") = (long)(arg1);                         \
    register long _arg2 asm("a1") = (long)(arg2);                         \
    register long _arg3 asm("a2") = (long)(arg3);                         \
    register long _arg4 asm("a3") = (long)(arg4);                         \
                                          \
    asm volatile (                                                        \
        "ecall\n"                                                     \
        : "+r"(_arg1)                                                 \
        : "r"(_arg2), "r"(_arg3), "r"(_arg4),                         \
          "r"(_num)                                                   \
        : "memory", "cc"                                              \
    );                                                                    \
    _arg1;                                                                \
})